rclone ( http://rclone.org ) is the perfect tool for that. It is a command line program which tries to work like rsync except copying to cloud storage providers (Dropbox, Amazon Drive, S3, Google Drive, B2 etc) . By default it will copy the files 1:1 file to remote object.
I use it to share stuff on Dropbox. I run Linux and have never installed the Linux client (if there is one, I don't know!)
PS I wrote rclone!
Syncthing is great if your goal is to synchronize files between different machines. However, if you want to share files/folders with people who do not have a strong tech background it's not really an option.